Kayentavenator (meaning "Kayenta hunter") is a genus of small carnivorous tetanuran dinosaur that lived during the Early Jurassic Period; fossils were recovered from the Kayenta Formation of northeastern Arizona and were described in 2010. Description The holotype specimen of K. elysiae is a juvenile, as shown by unfused neural spines and would have stood about high at the hip. The adult size of Kayentavenator is unknown. The inclusion of a pubic fenestra is one of the characteristics that Gay uses to set Kayentavenator apart from the contemporaneous, and better known Dilophosaurus. As Dilophosaurus lacks a pubic fenestra as a subadult or an adult, it is unlikely that it had one during any stage of ontogeny. Apomorphies include an ellipsoid acetabulum, the greater trochanter and the head of the femur having been fused, a mediodistal crest that extends 50% of the length of the femur, as well as a prominent accessory condyle on the medial femoral condyle, a groove in dorsal surface of the femoral head that extends out from the centerline of the body, and highly constricted ("waisted") caudal vertebra centra. Discovery The only known fossils of Kayentavenator were excavated by the University of California Museum of Paleontology from the Navajo Reservation in Arizona. It was briefly described in 2003 and was fully described in 2010 based on a partial fossil skeleton, consisting of part of the pelvis, partial hindlimbs, and vertebrae. Relationships Timothy Rowe originally assigned the holotype specimen of Kayentavenator to the coelophysoid Syntarsus kayentakatae (now Megapnosaurus kayentakatae or Coelophysis kayentakatae). It is unlikely that Kayentavenator is actually congeneric with Megapnosaurus kayentakatae due to the number of tetanuran characters that Kayentavenator possesses and M. kayentakatae lacks, such as the pubic fenestra and a sharp ridge on the medial side of the tibia. A cladistic analysis of the remains showed Kayentavenator to lie outside of Coelophysidae, and was closer to Allosaurus. This would make Kayentavenator the oldest known tetanuran from North America. The fragmentary remains of Kayentavenator make this open to further interpretation. Paleoecology Habitat The only known specimen of Kayentavenator, UCMP V128659, was recovered from the Silty Facies Member of the Kayenta Formation, in northeastern Arizona. A definitive radiometric dating of this formation has not yet been made, and the available stratigraphic correlation has been based on a combination of radiometric dates from vertebrate fossils, magnetostratigraphy, and pollen evidence. It has been surmised that the Kayenta Formation was